1. Technical Field
The present invention relates to fluid supply devices that supply fluid from a main tank through a subtank to a head, to printing devices, and to methods of controlling fluid supply devices.
2. Description of Related Art
One example of a fluid supply device is a device that is incorporated in a printer connected to a personal computer, and supplies fluid ink to the print head.
Japanese Unexamined Patent Appl. Pub. JP-A-2001-270133, for example, teaches a fluid supply device having a subtank unit that receives ink from an ink cartridge mounted on a carriage to an ink supply tube into a storage chamber, and supplies ink from the ink storage chamber to the recording head during printing; a pumping means that supplies ink from the ink cartridge to the subtank unit; and a pump control unit that controls ink flow according to a drive signal to the recording head.
Because of the complexity and installation space required by the construction of this pumping means, methods of using the bidirectional movement of the carriage to supply ink for simplification and saving space are also known from the literature. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2007-160639.
The ink supply device taught in JP-A-2007-160639 has a carriage that moves bidirectionally, an ink cartridge that stores the ink supplied to an inkjet recording head disposed to the carriage; an ink holding unit that holds the ink consumed for printing by the inkjet recording head; and an ink pump unit that is compressed and feeds ink to the ink holding unit as a result of the carriage moving to a specific position, and recovers and pulls ink from the ink cartridge as a result of the carriage moving to a position away from this specific position.
An ink supply device that works by compressing the ink pump unit using the drive power of the bidirectional movement of the carriage has an ink holding unit, which is a separate tank used as a buffer to store the ink from the ink pump unit. The ink holding unit tends to increase the size and cost of the ink supply device.
A configuration that draws ink from the ink cartridge by using the drive power of the bidirectional movement of the carriage to cause the ink pump unit to expand is used to simplify the construction because this configuration does not require a separate buffer tank. With this configuration the time required to inflate the ink pump unit increases as the amount of ink remaining in the ink cartridge decreases and the negative pressure increases. If the ink supply time is set referenced to a condition in which the remaining ink level is low, however, the ink supply time is longer than necessary when sufficient ink is left in the ink cartridge, and throughput is thus affected.